Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.94	4.591%	$161.0074	$161.01	$161.00	$161.00
Purchase #2	$127.27	9.596%	$139.4828	$139.48	$139.50	$139.50
Purchase #3	$59.78	11.730%	$66.7922	$66.79	$66.80	$66.80
Purchase #4	$62.33	6.215%	$66.2038	$66.20	$66.20	$66.20
Purchase #5	$128.62	6.780%	$137.3404	$137.34	$137.35	$137.30
Purchase #6	$105.81	12.411%	$118.9421	$118.94	$118.95	$118.90
Purchase #7	$233.90	12.678%	$263.5538	$263.55	$263.55	$263.60
7 purchase totals =	$871.65		$953.3225	$953.31	$953.35	$953.30